In the past, exterior walls of buildings were commonly constructed of solid masonry, involving multiple wythes (or thicknesses) of masonry laid up together. Floor joists were supported in recesses in the inner masonry wythe and floors, room partition walls, and the rest of the inside of the building were supported on these joists. In some cases, insulation was installed between wythes.
In the past few decades, solid masonry wall construction has been replaced by masonry veneer wall construction. For example, in single family residential construction, a frame of a house is constructed, usually of wooden studs, sheathing material is affixed to the outer surface of the studs and a single masonry wythe (often brick) is erected as a veneer outside of the sheathing material. In residential construction, insulating material is most often installed in the space between adjacent wooden studs. The masonry veneer wall is attached to the back-up wall of wood studs using an array of anchors. Each anchor terminates at its outer end as an embedment within the mortar bed between the rows of masonry, placed as the wall is erected. The inner end of each anchor is usually nailed to a wooden stud in the back-up wall framing.
More recently, especially in commercial buildings, the back-up wall to which the masonry veneer is attached has been made of steel studs and some, or all, of the insulating material is installed outboard of the steel stud framing. In this form of masonry veneer construction, the attachment between the studs and the masonry also involves an array of anchors. These anchors are commonly one-piece formed steel, with a slot or set of holes near the outer end of the anchor. In one common form of attachment, the anchor resembles a bayonet that is fastened to the steel stud and pierces the exterior sheathing (and any other materials outboard of the steel stud wall). In such a case the inner surface of each anchor can be screwed or bolted to a steel stud. A bent tie is inserted through slots or holes in the outer end of the anchor and then embedded in the mortar bed between rows of masonry.